In recent years, cluster storage devices have come into use. For example, one of the plurality of nodes of this type of storage devices that includes a disk device functions as a control node. When the control node receives an access request to data from a server, the control node specifies a node holding the requested data and notifies the server of it. This makes the server accessible to the node holding the target data.
Furthermore, known is a technique of transferring the function of the control node to another node depending on the load in the control node. For example, in the storage device, when the load on the control node is increased, a node with a low load is changed to be set as the control node (for example, see Japanese Laid-open Patent Publication No. 2010-146215).
Patent Document 1: Japanese Laid-open Patent Publication No. 2010-146215
Patent Document 2: Japanese Laid-open Patent Publication No. 10-177494
The above-mentioned technique, however, fails to reduce power consumption.
In the cluster storage device according to the above-mentioned technique, for example, when one node powers OFF functional units other than the disk device, the server becomes inaccessible to data stored in the node of which functional units have been powered OFF. For this reason, in the storage device, all the nodes power ON the functional units thereof even when the number of accesses to data is small and an input/output (I/O) load is low. This makes it impossible to reduce power consumed by the storage device.